Pump for precision adjustment



Jan. 19, 1954 E. e. MARTIN PUMP FOR PRECISION ADJUSTMENT 4 he'ets-Sheet 1 Filed Oct. 15, 1948 INVENTOR.

Jan. 19, 1954 E. G. MARTIN PUMP FOR PRECISION ADJUSTMENT Filed 001;. 15, 1948 4 Sheets -Sheet 2 INVENTOR.

Jan. 19, 1954 E. G. MARTIN 2,666,392

PUMP FOR PRECISION ADJUSTMENT I Filed on. 15, 1948 4 Sheets-Sheet s INVENTOR.

WW, gum Wm Jan. 19, 1954 e. MARTIN 66,

, PUMP FOR PRECISION ADJUSTMENT Filed Oct. 15, 1948 4 Sheets-Sheet 4 F I 0 (CF I INVENTOR.

Patented Jan. 19, 1954 S- PAT OFF I CE 2,666,392 PUMPFOR PRECISIbN ADJUSTMENT Edward G. Martin, GambridgeeMasst Application October 15, I Q4'8QSeriaINo. 54,694

3 Claims.

, P I V The present invention relates to" pumps and more particularly topumps for precision adjustmenr of the quantity ofmat'eri'a-I handled.

object of the present invention is to provide a pump particularly suited for laboratory and experimental use in which the fi'ui'd handled, whether a liquid or gas; maybeprecisel'y adjusted as toquantity;

Another object of the present invention isto v provideapump' in" which the fluid is scavenged from the cylinder atithe end of each stroke regardless" of the stroke. adjustment.

With'this'objectiir' view the principal feature of the present invention comprises a reciprocating." pump. having: a linkage: foroperating the piston arrangedsorthatthestroke may be varied entirely from one end of the cylinder whereby the clearance between the piston and the cylinder, at: the" end" of the" stroke is small and substantially uniform. Another feature contemplates means" whereby the stroke may' bevaried even during operation of the pump by simply changing the'position of" a fulcrum.

-In the accompanying'drawihgs' Fig. I. is a side elevation of'mypreferred'form of pump; Fig. 2

is a plan view Fig. 3 is a'section on line 3-3 of Figyl'; Fig: 4* is a section on line 4--4' of Fig. 1 Fig. 5*isa detail view ofthe'beam; andiFfig: 6 is a diagram 'ofthelinkage:

The illustrated embodiment of the present invention comprises a pump having a cylinder 6 within which reciprocates a piston 8. At the end of the cylinder is a valve box I0 containing rotary valves of any suitable construction. Connected with the valve box are an inlet port l2 and four outlet ports I4, the latter being under the individual control of manual valves l 6. The pump is driven by a motor [8 through a variable speed gear box 20, gears 22 and 24, and a crank shaft 26, the latter passing through the valve box It! to operate the valves and protruding at the other end for connection with the pistondrive linkages which are shown schematically in Fig. 6.

Referring first to Fig. 1, the crank shaft 25 is provided with a crank 28 connected through a link 29 with a walking beam 30 which extends along the entire side of the pump. The beam 30 is pivoted on an adjustable fulcrum pin 32 which will be described latter. The beam is provided with a long slot 34 to accommodate the pin. The slot extends to the extreme end of the beam, as shown in Fig. 5. The beam is strengthened at its outer end by a yoke member 36 which is spaced away from the beam proper by a sufiicient 2 distance-to allowthe-fulcrum pin 32 to-be moved to the-extreme end or the beam. The pin 3'? is provided with a flange 3 1 which can be accomm'o'dated in the space 38 within the yoke when the fulcrum; isat the" extreme end of the beam.

Pivoted to theyoke'36 is alink 40 which in turn is pivoted toa bellcrank having arms 42 and 44. The bell crank is journaled at a fixed point 45 of" the frame.- The arm 44 is pivotally connected to a piston d-ri'ving link 46 which is connected at 4! to the piston 8 itself.

link 48' is connected from afixed point 49 on" the frame to the yoke;

The fulcrum pin 32 is providedwith' a stud 56 mounted to slidein: a horizontal slot 52 in the frame. A screw 54 threaded through the stud isarranged for rotatable adjustment by a handwheel 56 to permit longitudinaladjustment of the fulcrum. A look screw 60 is preferably provided for the fulcrum. An index $2 is mounted on the fulcrum and moves over a graduated scale 64% The operation of thepum'pis explained in conjunction with the simplified linkage diagram of Fig; 6.- I-h this diagram the various links are shown in single lines, but withthe same reference characters" asinthe actual structure. Certain' points are' conveniently designated by letters as f'ollows z crankshaft aX-isA; crank pin- B; left end-"of beam 30'; C'; connection oflink 46 topi'ston, D; fulcrum 32, E; fixed point 49, F; pivotal connection between 44 and 46, G; right end of beam, H; end of bellcrank arm 42, J; journal 45 mounting for bellcrank, K. For one position of the crank pin B, the foregoing letters are used; for another position certain of the parts are shown in dash lines and the letters are primed.

When the pin B is at its lowermost position, the beam 30 is horizontal and the points C, E, F and H are at that time all in a straight line. Horizontal orientation of the beam 30 is of course not essential but it is necessary that the points C. E. F and H all lie on a straight line, which line coincides with the fulcrum guide slot 52; thus the fulcrum point E, whatever its adjusted position, lies on. that line.

For the full-line condition, the piston 8 is at the limit of its compression stroke. When the crank makes a half revolution so that point B is carried into B, the walking beam is tilted about the fulcrum point E so that points C and H assume the positions indicated. As a result the piston is brought to the limit of its suction end of the beam and a fixed part of the frame; thus the end of the beam follows a circular arc, of which E is always its center, and the length of the arc is determined by the setting of the fulcrum.

To shorten the stroke of the piston it is only necessary to move the fulcrum E along the horizontal line to any desired point. The point E can in fact be moved to the right until it coincides with H, under which condition the stroke is zero. The zero condition is permitted because the fulcrum pin 32 is adjustable to the extreme end of the beam by reason of the yoke 36.

It will be observed from Fig. 6 that the limit of the compression stroke (shown in full lines) of the piston is always the same, regardless of the setting of the fulcrum; that is, the effect of changing the fulcrum is to only change the suction stroke. Since the full-line position is the position of minimum clearance, this results in a substantially complete scavenging of the pump cylinder on each compression stroke. If the pump is being used to handle several diiierent fluids in succession, as in certain experimental studies in animal aeration, the shift from one fluid to another is accomplished with assurance of satisfactory scavenging. I

The stroke may be varied at any time, even when the pump is running, by loosening the lock screw and turning the handwheel to move the fulcrum.

Having thus described my invention, I claim:

1. A pump comprising a cylinder, a piston, a linkage for driving the piston, including a walking beam, 9. fulcrum therefor, a support for said fulcrum along which the fulcrum is adjustable, a crank for rocking the beam, a link pivotally connected to the beam for actuating the piston, and a rigid member pivotally-connected at one end to the beam and at the other end to the support for longitudinally positioning the beam during rocking movement, the fulcrum being adjustable along a line so oriented that the position of the beam is unchanged when the beam is at the limit of its rocking movement on the compression stroke of the piston.

2. A pump comprising a cylinder, a piston, a linkage for driving the piston, including a walking beam, 2. fulcrum therefor, a support for said fulcrum along which the fulcrum is adjustable,

a crank for rocking the beam, a link pivotally connected to the beam for actuating the piston, and a rigid member pivotally connected at one end to the beam and at the other end to the support for longitudinally positioning the beam during rocking movement, the fulcrum being adjustable along a line so oriented that the position of the beam is unchanged when the beam is at the limit of its rocking movement on the compression stroke of the piston, the beam having a slot for said fulcrum extending to the region of the pivotal connection of the piston-actuating link to permit the fulcrum to be adjusted to a point coaxial with said link pivot to reduce the pump stroke to zero.

3. A pump comprising a cylinder, a piston, a linkage for driving the piston, including a walking beam, a fulcrum therefor, a support for the fulcrum along which said fulcrum is adjustable, a crank and link for rocking the beam, a second link pivotally connected to the beam at a point remote from the crank link for actuating the piston, means independent of said links for longitudinally positioning the beam during rocking movement, a slot in the beam within which the fulcrum is received, and. means for adjusting the fulcrum in the support and along the beam to vary the center about which the walking beam is rocked by the crank, the paths of adjustment of the fulcrum in the support and along the beam being coincident when the beam is at the limit of its movement on the compression stroke.

EDWARD G. MARTIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 216,752 Olsen June 24, 1879 536,430 Higgins Mar. 26, 1:895 552,386 Mofiatt Dec. 31, 1895 762,055 Hibbard June 7, 1904 1,189,312 Tibbels July 4, 1916 1,191,453 Myers July 18, 1916 1,217,333 Myers Feb. 27, 1917 1,292,457 Hall Jan. 28, 1919 2,197,730 Mugford Apr. 16, 1940 2,259,713 Valentine Oct. 21, 1941 2,423,162 Summers July 1, 1947 

